This invention lies in the field of heat transfer apparatus. More particularly, it concerns gas to gas heat transfer apparatus.
Still more particularly, this apparatus is concerned with heat transfer from hot flue gases, particularly those that may contain sulfur oxides, to cold air to be used for combustion purposes. The particular factors involved concern the design of the apparatus to prevent cooling any part of the metal surfaces below the dew point of the flue gases, particularly when containing sulfur trioxide, so as to avoid corrosion troubles.
In the prior art, there have been many designs of gas to gas heat exchange devices. However, because of the importance of energy conservation at the present time, and because of the necessity of using fuels that contain sulfur, and the importance of reducing the corrosion which results when sulfur trioxide-containing flue gases are cooled below the dew point, various features of this invention will obviate many of the difficulties previously experienced in equipment of this sort because of the corrosion due to sulfuric acid formed when SO.sub.3 reached dew point temperature in the presence of water vapor.